Osteoporosis Urine Mineral Screen

Indications:

Urine calcium can be used in the assessment of vitamin D status; if the serum vitamin 25-hydroxy cholecalciferol is > 200 nmol/L and the UCa/Cr is > 0.60, that is evidence for vitamin D toxicity. An increase in osteoclastic bone resorption will also raise the UCa/Cr. Vitamin D deficiency, or a calcium-restricted diet, may reduce the UCa/Cr ratio to < 0.25. Low sodium diets tend to decrease UCa/Cr, while a high sodium intake and excretion increases UCa/Cr.

Urine phosphate is more influenced by diet than is urine calcium because of the greater proportion of dietary PO4 absorbed from the gut. High circulating vitamin D and PTH cause phosphaturia by increasing the renal clearance of phosphate.

Phosphaturia also causes loss of magnesium in the urine. A low Mg value in an e.m.u. suggests magnesium deficiency, but a normal result does not exclude magnesium deficiency, which can be checked by measuring red cell magnesium.

A wide reference interval for urine zinc reflects the poor intake of zinc in many subjects. Zinc is required for both osteoblastic and osteoclastic activity.

Patient Instructions:

Provide a second void early morning urine sample (I.e. a 20-30ml aliquot of urine from the second sample passed in a morning before you take any nutritional supplements).